Just being around the lead based paint won't hurt them.Majority of the houses here were built before 1978 and t's too expensive to de-lead them - some neighborhoods MV is around $50-60K.

Say we have around $100k to put in, we could put 25% down (standard around here for a conventional mortgage on second/investment home) on either 1 $400k home, 2 $200k condos, or 1 less expensive place needing repairs (putting some of our capital against renovation).

I decided to rent my 2 extra rooms to house hack, greatly reducing my expenses.

Even the most expensive laminate and vinyl options are $3 psf, which is $2,400 for the 800 square feet which require that. 

You'll need a couple months to cover expenses but it does depend on the financing company that you use.

The builder's risk and vacant dwelling policies are expensive and cumbersome to get for each property individually.

All finishes are going to be mid grade stuff, fairly durable but not too expensive.

That gets expensive quick .   

I don't know your market at all, but right now for the most part, building is way too expensive for investments sadly. 

Counterproductive to your end game.Roll the IRA into a self directed version and buy the property with IRA funds (you can get a non recourse loan too).As @Christopher Phillips mentioned, every property needs to cash flow with at least 70% financing or it is not a good deal from a cash flow perspective.Also, this $700 or so cash flow you are quoting, does that take into account all the expenses?